Radio Access Network (RAN) sharing deployment scenarios are known and methods and abilities to facilitate implementations of these scenarios have been introduced into the 3G standards since Release 5.
RAN sharing provides a way for network operators (service providers) to reduce their capital expenditure requirements and/or widen the area covered by a cellular communication service when setting up a wireless communications network. Rather than each operator having to provide their own base station and associated equipment for each cell of the network, an operator sharing the RAN of another operator is able to provide their service into areas served by the other operator without having to invest in their own base stations in that location.
Furthermore, by reducing the number of base stations that must be provided and operated, the ongoing operating costs can be reduced for the sharing operators. Indeed, each base station may draw a large amount of electricity during operation, and therefore reducing the number of operating base stations may significantly reduce electrical power requirements and may therefore also be considered environmentally friendly.
In some shared schemes, only the RAN base stations themselves are shared by the different operators. In other shared schemes, parts of the core network, for example the Evolved Packet Core (EPC) in LTE, can be shared as well as the RAN base stations, further decreasing capital expenditure costs in setting up the network.
The mechanisms for sharing of RANs may also be useful in the case of mergers of operator companies, allowing the two operators to merge their network services without any significant interruptions in service provision.
LTE base stations and their associated core networks provide a packet switched service and do not support circuit switched services such as voice calls. Therefore, when a user of a mobile phone (or another piece of so-called “user equipment” (UE) such as a portable digital assistant) wishes to make a voice call on an LTE network, it is necessary for the phone to “fall back” onto an alternative network which exists in parallel with the LTE network and which does support voice calls. Examples of such alternative networks are Code Division Multiple Access (CDMA) networks, such as CDMA2000 (C2K) networks or UMTS networks. A similar fall back procedure is also performed in other situations, such as for SRVCC (single radio voice call continuity) whereby a VoIP call is handed over from the LTE network to the UMTS/CDMA2000 network.